#define _CRT_SECURE_NO_WARNINGS 1
#include<iostream>

using namespace std;

int fact(int n)
{
	if (n < 3)
	{
		return 1;
	}
	else
	{
		return fact(n - 1) + fact(n - 2);
	}
}

int main()
{
	int n;
	cin >> n;
	cout << fact(n);
	return 0;
}